Definition
Peripatidae is a family of onychophorans, commonly known as velvet worms, within the phylum Onychophora. Members of this family are terrestrial, soft-bodied invertebrates characterized by a segmented, annulated body and numerous paired, stubby limbs.
Overview
Peripatidae comprises a diverse group of velvet worms primarily distributed in tropical and subtropical regions of the Southern Hemisphere, including parts of Africa, Southeast Asia, and the Neotropics. The family is one of two principal lineages within Onychophora, the other being Peripatopsidae. Species in Peripatidae exhibit ovoviviparous or viviparous reproduction, differing from the oviparous reproductive mode typical of many Peripatopsidae. The family currently includes roughly 30 genera and over 100 described species, though taxonomic revisions are ongoing.
Etymology/Origin
The name “Peripatidae” derives from the Greek word peripatēs (περιπατής), meaning “walker” or “one who walks about,” reflecting the organism’s locomotion via numerous fleshy legs. The suffix “-idae” is a standard zoological ending denoting a family-level taxon.
Characteristics
- Morphology: Adults possess an elongated, soft body ranging from 1 to 15 cm in length. The cuticle is thin and bears a velvety texture due to microscopic papillae. The body is divided into a head region and a series of homonomous segments, each bearing a pair of unjointed, lobopodial limbs equipped with adhesive papillae for prey capture.
- Reproduction: Most Peripatidae species are viviparous, with embryos developing within the female’s uterus and receiving nourishment via a placenta-like structure or yolk. Some exhibit ovoviviparity, where eggs hatch within the mother’s body.
- Sensory Organs: They possess a pair of simple eyespots (ocelli) on the head, along with numerous antennal-like papillae that serve somatosensory functions.
- Ecology: Typically inhabiting leaf litter, rotting wood, and moist forest floors, Peripatidae are predatory, feeding on small arthropods and other invertebrates captured using a rapid ejection of adhesive slime from oral papillae.
- Physiology: Their nervous system consists of a ventral nerve cord with segmental ganglia. They lack a true coelom, possessing a hydrostatic skeleton that facilitates movement.
Related Topics
- Onychophora – the phylum encompassing all velvet worms, including both Peripatidae and Peripatopsidae.
- Peripatopsidae – the sister family to Peripatidae, primarily distributed in temperate regions of the Southern Hemisphere.
- Lobopodia – a group of basal panarthropods sharing lobopodial limbs with onychophorans.
- Venomous slime – the adhesive secretion used by velvet worms for prey capture and defense.
- Evolutionary significance – Peripatidae provides insight into the early diversification of panarthropods and the transition from marine to terrestrial habitats.